Fear not, your Work Unit total is not lost. The Seti classic WUs stats are moved across to your BOINC account information. It is not done very often so the stats for seti classic in your BOINC account info will look old. If you migrated after 15th March (last update) it will read zero.

For sure Boinc will copy over the SETI classic stats for a final time when SETI classic is finally closed down. I do not know if they will do another update before the close down. In the interim have a look at one of the many stats add-ons: e.g. the one I use boinc synergy at http://www.boincsynergy.com allows you to setup signatures with all BOINC project stats and your SETI classic WU count.